1. Field of the Invention
This invention relates to internal combustion engines for ground-moving vehicles, and more particularly, to a fuel heat transfer assembly for controlling fuel temperature to an internal combustion engine of a ground-moving vehicle.
2. Description of the Prior Art
Presently ground-moving vehicles having internal combustion engines operate over a wide range of external temperature conditions requiring diverse methods to maintain fuel quality and temperature. In summer months, internal combustion engines employing fuel injector systems commonly maintained fuel temperatures at lower levels by circulating the fuel from the fuel tank to the fuel injector pump to the fuel tank, basically mixing hot fuel from the injector pump with the cool fuel in the fuel tank. Such method may not be effective for many vehicle applications, particularly, for over-the-road trucks, since the fuel tank is now being positioned behind aerodynamic flaring units thereby blocking air flow. Elevation of fuel temperatures in the fuel tank to unacceptable levels, e.g., up to 140.degree. F. result in poor engine performance and potential malfunction, particularly where new generation of diesel engines require fuel to cool engine electronics. Elevated fuel temperatures also effects mass flow fuel and volume to both a carburetor as well as fuel injection systems thereby decreasing engine performance as a function of fuel temperatures.
Another method to reduce fuel temperatures is the use of a heat exchanger assembly through which ram air is passed; however, placing a limitation on outside ambient air temperatures, i.e., at about 115.degree. F., whereas it is impossible to reduce fuel temperature below 115.degree. F. Additionally, at low temperatures, such a heat exchange assembly is not useful for raising fuel temperatures at low outside ambient air temperatures. During winter months, fuel oil may gel if not chemically treated or warmed. Chemical treatment may cause engine damage since most additives remove natural lubrication from diesel fuel.
Pre-heating assemblies for fuel for cold periods are accomplished by electric or engine coolant systems which are expensive to install and require a second system to keep fuel cool in summer months.
Temperature of the fuel to be used by an internal combustion engine is critical to engine performance. For fuel injection systems, elevated temperatures decrease fuel density (or its mass), making injector pump volume and compression more difficult. As fuel density decreases, so does the fuel mass droplet size or flow resulting in lower spray penetration and injector rate.